This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to test fecal calprotectin as a possible inflammatory marker in patients with ankylosing spondylitis (AS) and as a correlate with serum markers for inflammatory bowel disease (IBD). The study population will include adult AS patients, who themselves or a first degree relative do not have (IBD), as cases, and healthy adult volunteers without IBD as controls. Cases will be randomly selected from the PSOAS study (Prospective Study of Outcomes in Ankylosing Spondylitis) cohort and recruited via phone and mail, and volunteer controls will be recruited from the Los Angeles area. If the subject agrees to participate in the study, he/she will be mailed a consent form and stool sample kit, and asked to bring both items to the study visit where we will also answer any additional questions, collect one serum sample, and provide a self-administer questionnaire. There is only one study visit per subject.